Apparatus for dimpling sheet material and preheating the area to be dimpled



,APPARATUS FOR DIMPLING SHEET MATERIAL AND w w. WILLIAMS 2,424,643

PREHEATING'THE AREA TO BE DIMPLED v Filed Feb. 14, 1945 2 Sheets-Sheet 1 v 'INVENTOR WILLIAM W. WILLIAMS w, M M A'ITQRNEYS July 29, 1947. A w w, WILLIAMS 2,424,643

APPARATUS FOR DIMPLING SHEET MATERIAL AND PREHEATING THE AREATo BE DIMPLED Filed Feb. 1 1945 2 Sheets-Sheet 2 lNVENTOR WuLup W. WILLIAMS 01 .6011, ATTORNEYS Patented July 29, 1947 APPARATUS FUR DIMPLING SHEET 'MATE- RIAL AND PREHEATING' THE AREA TO BE DIMPLED "Wi1liam'W. Williams,'Bufialo, N. Y., assignor to Bell "Aircraft Corporation, BuffalmN. Y.

ApplicationsFebruary 14, 1945, Serial No. 577,893

s'claims. 1

This invention relates to metalpressingzmethods and means, such as are adaptable toparticular advantage, for example, to sheet metal dimpling and like operations. More particularly the invention relates to an improved method and means for locally forging cold sheet metal stock pieces and the like, as in connection-with large manufacturing operations.

One of the objects of theinvention-is to provide an improved method and means for forging or pressing shop stock pieces into reformed shapes. Another object of the invention is to provide an improved forging method and means such as is adapted particularlyto provide improved results in connection with rapid multiple pressing operations. Another object of the invention is to providean improved methodand means for forging thermoplastic stock pieces, such as is particularly suitable for example to provide multiple local deforming operations at rapid rate.

Another mOre specific object of the invention is to provide an improved die type mechanism for locall forging cold sheet metal stock pieces and the like into reformedshapes. Another object of the invention is to provide animproved. method and means for .dimpling sheet metal stock pieces at rapid rate while reducing the stock material fracturing tendencies. .Another more specific object of the invention is'toprovide an improved method and means for dimpling stock which is normally difficult to handl-e such as aluminum and magnesium alloy stock sheets and the like. Other objects and advantages-of the invention will appear in the specification hereinafter.

In the drawings:

Fig, 1 is a fragmentary elevation largely in section, of an apparatus of the invention; and

Fig. 2 is a fragmentary elevation, also largely in section, of another form of the apparatus'of the invention.

The drawing illustrates a so-called .di-mpling" process being applied to a work sheet which is designated generally at for the :purpose of locally forging the work sheet as at'the region of the drilled holes therein so as to formrcountersinks or dimples such as will adaptth'e work sheet to receive the conically shaped heads of rivets or the like in flush relation withthe top surface of the work sheet lll asviewedin Fig. 1.

In certain arts, as for example inthe aircraft manufacturing art, large quantities of multiple drilled and countersunk work sheets of the character of the .work sheet :IU of the .drawingrare 2 required; and such work sheets are often formed of special alloys designed to provide such sheets to be extremely light Weight yet of sufficient strength and rigidity to successfully withstand the loads to be imposed thereon. Suitable alloys for such purposes usually include the aluminum and magnesium type alloys such as are relatively nonemalleable at normal temperatures.

when in cold condition without fracturing and tearing the stock material in the region of each forging operation. Yet it is undesirable to overall heat such work sheets prior to such dimpling operations because such overall heating renders the work sheets soft and unstable and subject to twisting and wrinkling distortions during the handling operations incidental to transferring them from the heating operation to the dimpling operation. Also, such overall heating methods are undesirable because of the additional step involved thereby and the extra facilities required to perform such operations; and because of the extra time and expense incidental thereto.

The present invention obviates the objections and disadvantages referred to hereinabove by providing the work sheet to be rapidly heated locally and exactly at the regions of the forging operations to be performed; the heat being thereby focalized upon only the portion or portions'of the sheet required to be heated so as to bring such portions rapidly to the optimum temperature for the forging operations while avoiding overall weakening of the work sheet structure.

With'the above purposes in view the apparatus of the invention may comprise, as illustrated in the drawing, an upper die It and a lower die l8 arranged in opposing relation to receive the work sheet to be dimpled therebetween. Any suitable means for providing relative movement between the dies !Gl8 may be employed, but as illustrated in the drawing the upper die is may be carried by a ram stem 20 so as to be adapted to be alternately pushed and pulled toward and away from the lower die is. The die [8 is centrally countersink bored at 22 and a complementary shaped boss 24 extends from the die l6 and is adapted to be inserted through the openings drilled in the work sheet as at 25 (Fig. 1) preliminary to performance of the dimpling operation; whereby each drilled portion of the work sheet will be automatically centralized relative to the dies when penetrated by the pilot boss 24. The upper end of the boss 24 is conically shaped as indicated at 26 to complement the shape of the counterbore 22 in the die Hi.

Therefore, it isdiiilcult to dimple such work sheets Thus, it will be understood that upon application of power to the ram 20 the upper die 16 will be forced so as to first insert the boss 24 through the work sheet l and then to press the material of the stock piece surrounding the aperture through the sheet downwardly into the countersink portion 22 of the lower die [8, thereby forming the material of the stock piece into the form of a dimple for the purpose hereinabove stated.

To provide local mallea'bilizing of the stock piece such as is required to prevent fracturing thereof in connection with each dimpling operation, the die I is provided with heat supply means in the form of a conduit comprising the hollow interior 30 of the die ending in gas passages 3233 directed to discharge hot gases from the die chamber 30 in such manner as to flood the spot on the stock piece which is to be dimpled; and means are provided for blasting a heating fluid medium into the die chamber 38 as required incidental to each dimpling operation.

For example, as illustrated in Fig. l, the die l8 may be mounted upon an open end conduit 35 to be connected in open communication with the interior thereof. A gas jet such as illustrated at 38 is arranged interiorly of the conduit 35, and the jet 36 may be arranged to burn any suitable heating gas or other fuel such as supplied by a gas producer or other Public utility or the like. The conduit 35 is arranged at its end 38 to take in air to furnish oxygen for combustion of the gas, and to normally discharge the products of combustion at its other end 39 into the atmosphere. Thus, it is arranged that a gas flame will normally extend as indicated at 40 within the interior of the conduit 35; and a gas flow control device is arranged in conjunction with the conduit feeding the jet 36. Hence, whereas normally only a pilot flame burns as at 49, the rate of gas flow may be increased at will by the operator so as to extend the flame as at 42 beyond the position of the opening 30 in the die IS in connection with each dimpling operation. An air blast tube 44 projects through a Wall portion of the conduit 35 diametrically opposite to the position of the opening 39 within the die l8, and the tube 44 is arranged to be fed with a supply of compressed air controlled by valve means so as to be intermittently operable to blast a supply of compressed air across the interior of the conduit 35 and into the chambered portion 30 of the die I 8 and thence out of the passageways 32-33 so as to be impinged against the bottom of the work sheet [9 in the immediate region of the dimpling operation to be performed.

Thus, whenever the gas pilot flame 40 is extended as to the position 42 coincidentally with delivery of an air blast through the tube 44, the chamber 30 within the die lit will receive an intensely hot pressured mixture of flaming gas and heated air, and jets of intensely heated gas will issue through the passageways 3233 and impinge against the .work sheet l0.

Thus, upon proper positioning of the work sheet upon the die IS, the operator may temporarily extend the gas flame, and project a blast of air through the gas flame into the interior of the die for preheating the stock piece preliminary to the dimpling operation. Following a predetermined time delay period the ram 20 may be operated to press the upper die into dimpling position against the work sheet, and upon completion of this operation the gas and compressed air valves 3'! and 4|, respectively, will be returned to inoperative positions while the ram 20 is elevated so as to free the work sheet from the dies.

Fig. 2 illustrates another form of apparatus of the invention wherein a work sheet 58 is shown to be resting in operative position upon a support collar 52 which telescopically rides upon the upper end of a stationary die '54 carried upon a base 55. The die 54 is formed at its upper end with a shank 56 terminating in a conical shoulder 58 and a work sheet positioning boss 68; and a compression spring 62 is disposed between the collar 52 and the die body 54 so as to bias the collar toward the elevated position thereof shown in Fig. 2. The travelling die is illustrated at 65 to be carried upon a tubular frame 66; the die 65 being bored as at 68-69 in open communication with the hollow interior of the tube 66. The die 65 is countersunk at 10 to complement the conical shoulder 58 of the lower die for forging the work sheet therebetween to provide a dimpled formation in the work sheet as explained hereinabove.

A gas jet 1.2 receiving its supply from a conduit H is disposed within the tube 66 to project a gas flame interiorly thereof as indicated at 73-44, and an air blast jet 75 is formed at the end of an air conduit which is coiled at 16 to provide a preheating conduit disposed interiorly of the tube 68 and arranged to be fed through an air supply conduit 13 from any suitable source of pressured air. The tube 65 is mounted upon the lower end of a ram 88 which may be arranged to be motivated toward and away from the lower die by any suitable mechanism as will be understood by anyone versed in the art.

The gas and compressed air jet supply conduits will preferably be equipped with suitable valve means 8| and 82, respectively, whereby the gas flame may be extended and the compressed air blast projected through the gas flame into the interior of the upper die 65 and thence through the outlet port 69 thereof for impingement against the work sheet 50 at the immediate location of the dimple to be formed therein. Also, as in the case of the arrangement of Fig. 1, the ram actuating mechanism will preferably be operated so as to bring the die devices together following a proper heating of the stock piece; and the gas and air valves may be operated following the positioning of the work sheet 50 upon the boss 60. It may of course be arranged that cessation of the heating operation and retraction of the upper die may be provided either automatically or by further manual manipulation of a control device, as is preferred. It will be understood that upon movement of the upper die 65 into pressing position against the stock piece 50 the first reaction will be a downward retreating of the collar 52 against the action of the spring 62 until the conical shoulder portion 58 of the lower die bears upwardly against the stock sheet 50 and presses it into the countersunk portion 1a of the upper die. Thus, a particular feature and advantage of the invention is that each local heating operation which is performed by synchronous operation of the control valves is followed by the local forging process, whereby the work sheet may be momentarily brought up to optimum forging temperature without requiring an undesirable elongation of the maximum heating period. I have determined that heated air and gas mixtures may be used with particular advantage for the stock piece heating medium as illustrated and described hereinabove whenever the stock pieces being fabricated are, for example, of relatively thin sheet and rapid heat transfer form. It seems that the use of hot gases for this purpose makes it possible to provide extremely flexible temperature control such as to almost spontaneously procure optimum forging temperatures at the areas-to be forged while avoiding producing annealing temperature conditions in the stock sheets such as would adversely affect the stock sheets for the purposes for which they are intended.

Advantages attending use of the apparatus and method of the invention include improved accuracy of stock sheet heating control; elimination of tearing or cracking or other fracturing tendencies in the portion of the stock sheet being forged; elimination of markoff in both the formed dimple and in the body of the stock sheet; avoidance of overheating of the dies and die actuating parts such as springs or the like which are usually employed in connection with the die actuating mechanisms; protection of the operator against injurious heat exposures; and overall increased speed of operation.

Although only one application of the method of the invention and only two forms of the apparatus thereof have been illustrated and discussed in detail, it will be understood that the invention is also applicable to various other manufacturing operations and that various changes may be made in the apparatus as disclosed herein without departing from the spirit of the invention or the scope of the claims.

I claim:

1. An apparatus for dimpling sheet metal stock, said apparatus comprising opposed dies having forging face portions adapted to engage the stock at restricted regions only, one of said dies having a central bore directed against the other die, means for projecting a stream of hot liquid across the open end of the bore of the die and substantially normal to the axis thereof, and means for intermittently diverting said stream and projecting it into the die bore and locally against the workpiece.

2. An apparatus for dimpling sheet metal stock, said apparatus comprising opposed dies having forging face portions adapted to engage the stock at restricted regions only, one of said dies having a: central bore directed against the other die and a plurality of apertures extending from the bore to the workpiece-engaging end of said one die, means for projecting a stream of hot liquid across the open end of the bore of the die and substantially normal to the axis thereof, and means for intermittently diverting said stream and projecting it into the die bore and locally through the apertures against the workpiece.

3. An apparatus for dimpling sheet metal, comprising an anvil die and a cooperating reciprocating die, each of said dies being formed with complemental working surfaces for dimpling an interposed workpiece, a horizontally arranged retort disposed on the side of the anvil die opposite the workpiece-engaging end thereof and having its axis substantially normal to the axis of said die, a gas jet disposed within the air inlet end of said retort for creating combustion therein, said anvil die being formed in its workpieceengaging surface with a plurality of apertures, and a compressed air jet communicating with said retort and having its axis substantially in alignment wtih said anvil die, whereby the gas flame and heated air in said retort is directed through the apertures of said anvil die and locally against said workpiece.

4. An apparatus for dimpling sheet metal, comprising an anvil die and a cooperating reciprocating die, each of said dies being formed with complemental working surfaces for dimpling an interposed workpiece, a horizontally arranged retort disposed on the side of the anvil die opposite the workpiece-engaging end thereof and having its axis substantially normal to the axis of said die, a gas jet disposed within the air inlet end of said retort for creating combustion therein, said anvil die having an axial chamber opening into said retort, said anvil die being formed in its workpiece-engaging surface with a plurality of apertures in-communication with the chamber of said die, and a compressed air jet communicating with said retort and having its axis substantially in alignment with said anvil die, whereby the gas flame and heated air in said retort is directed into the chamber and through the apertures of said anvil die and locally against said workpiece.

5. An apparatus for dimpling sheet metal, comprising an anvil die and a cooperating reciprocating die, each of said dies being formed with complemental working surfaces for dimpling an interposed workpiece, an axially arranged chamber formed in said anvil die, a plurality of openings formed in the workpiece-engaging end of said die in communication with said chamber, a heating device disposed adjacent said anvil die and having a gas flame projectable across the open end of the anvil die chamber, and an air jet for deflecting said gas flame into said chamber and out through the apertures of said anvil die for locally heating a workpiece interposed between said dies.

6. An apparatus for dimpling sheet metal, comprising an anvil die and a cooperating reciprocating die, each of said dies being formed with complemental working surfaces for dimpling an interposed workpiece, said anvil die being formed with an axial chamber and a series of apertures at its work-engaging end connected to the chamber, a horizontally arranged retort disposed on the side of the anvil die opposite the workpieceengaging end thereof, means for creating a normally low gas flame in said retort, means for intermittently increasing the length of said flame to project it across the opening of the anvil die chamber, and means for simultaneously projecting a stream of compressed air against said flame for forcing the tip thereof into the anvil die chamber.

WILLIAM W. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent: 

